1. Technological Field
This disclosure pertains generally to estimating focal distance, and more particularly to estimating focal distance in response to performing image defocusing.
2. Background Discussion
Blur matching is often utilized for estimating focal depth between two images. As the subject comes into focus, the captured image becomes the sharpest with its highest contrast (sharpest). Generally, when two pictures are taken at two different focus distances, the one captured closer to the subject distance is sharper than the other. The focus distances at which the pictures are taken and the amount of blur difference between these pictures can be utilized for estimating actual subject distance, or depth according to a focus model determined for that camera-lens system, such as by utilizing a step-edge image at different focal lengths.
Blur matching can be performed either with direct matching or indirect matching. The use of direct matching relies upon comparing pixel correspondence between the two images and makes a comparison of pixels in corresponding positions in the images being processed. In view of these direct pixel to pixel comparisons, direct matching is thus subject to significant issues when relative motion arises between the two images, and these issues become especially problematic in the case where rotational motion or shape changing arises between the two images. Indirect matching performs a comparison after some processing of the images, so that a direct comparison is not being made. However, attempts at using indirect matching have themselves failed to provide optimum results.
Accordingly, a need exists for an indirect blur matching apparatus and method which overcomes shortcomings of previous direct and indirect blur matching methods.